Cutaneous anthrax

Last updated: September 2022

Anthrax is caused by the bacterium Bacillus anthracis that primarily affects herbivores (sheep, goats, cows, camels, horses, etc.). Humans may become infected through contact of broken skin with a dead or sick animal. People at risk include livestock farmers and those that manipulate skins, wool or carcasses of infected animals.

The disease is found in Eastern Europe, Central Asia, the Mediterranean Basin, Africa and South America.

Pulmonary (acquired by inhalation) and intestinal (acquired by eating infected meat) forms also exist.

Clinical features

• Papule, then pruritic vesicle on uncovered skin surfaces (face, neck, arms, legs). The vesicle ulcerates and becomes a painless black eschar surrounded by oedema, often associated with with lymphangitis and regional lymphadenopathy.
• The following are criteria of severity:
  • lesion located on the head or neck, or
  • presence of systemic symptoms (fever, malaise, headache, tachycardia, tachypnoea, hypotension, hyper/hypothermia), or
  • presence of extensive oedema, or
  • multiple, extensive or bullous lesions.

Laboratory

• From vesicular fluid a Citation a. Samples can be stored (including transport time) for 7 days max. in cold chain (if not available, at a temperature < 30 °C). : culture and drug susceptibility testing (rarely available) or Gram stain for microscopic examination.
• PCR testing (reference laboratory).

Treatment

Uncomplicated cutaneous anthrax 

• Do not excise the eschar; daily dry dressings.
• Antibiotic treatment for 7 to 10 days:
  • First-line antibiotics:
    ciprofloxacin PO (including in pregnant or breastfeeding women and children)
    Children: 15 mg/kg (max. 500 mg) 2 times daily
    Adults: 500 mg 2 times daily
    or

doxycycline PO (except in pregnant or breastfeeding women)

Children under 45 kg: 2 to 2.2 mg/kg (max. 100 mg) 2 times daily
Children 45 kg and over and adults: 100 mg 2 times daily

• Alternatives include:

clindamycin PO (in patients allergic to first-line antibiotics)
Children: 10 mg/kg (max. 600 mg) 3 times daily
Adults: 600 mg 3 times daily

or

amoxicillin PO, if penicillins are effective (documented susceptibility)
Children: 30 mg/kg (max. 1 g) 3 times daily
Adults: 1 g 3 times daily

Severe cutaneous anthrax

• Combined antibiotic treatment for 14 days:

• First-line:
  ciprofloxacin IV infusion over 60 minutes b Citation b. Dilute each dose of ciprofloxacin, clindamycin or ampicillin in 5 ml/kg of 0.9% sodium chloride or 5% glucose in children less than 20 kg and in a bag of 100 ml of 0.9% sodium chloride or 5% glucose in children 20 kg and above and in adults. Administer ciprofloxacin more slowly than clindamycin or ampicillin.
  Children: 10 mg/kg (max. 400 mg) every 8 hours 
  Adults: 400 mg every 8 hours 
  + clindamycin IV infusion over 30 minutes b Citation b. Dilute each dose of ciprofloxacin, clindamycin or ampicillin in 5 ml/kg of 0.9% sodium chloride or 5% glucose in children less than 20 kg and in a bag of 100 ml of 0.9% sodium chloride or 5% glucose in children 20 kg and above and in adults. Administer ciprofloxacin more slowly than clindamycin or ampicillin.
  Children 1 month and over: 10 to 13 mg/kg (max. 900 mg) every 8 hours
  Adults: 900 mg every 8 hours
• Alternative, if penicillins are effective (documented susceptibility):

ampicillin IV infusion over 30 minutes b Citation b. Dilute each dose of ciprofloxacin, clindamycin or ampicillin in 5 ml/kg of 0.9% sodium chloride or 5% glucose in children less than 20 kg and in a bag of 100 ml of 0.9% sodium chloride or 5% glucose in children 20 kg and above and in adults. Administer ciprofloxacin more slowly than clindamycin or ampicillin.
Children 1 month and over: 50 mg/kg (max. 3 g) every 6 hours or 65 mg/kg (max. 4 g) every 8 hours 
Adults: 3 g every 6 hours or 4 g every 8 hours

+ clindamycin IV infusion as above.

Change to oral treatment as soon as possible to complete 14 days of treatment with ciprofloxacin + clindamycin or amoxicillin + clindamycin as for uncomplicated cutaneous anthrax.

• Intensive care: symptomatic treatment of shock (see Shock, Chapter 1); tracheostomy and ventilatory support may be necessary.

Prevention

• Antibiotic prophylaxis in case of known skin exposure: treat for 10 days PO as for uncomplicated cutaneous anthrax.
• Livestock vaccination; burial or burning of animal carcasses.